This invention relates to the art of treating an aluminum surface to improve the properties thereof. More specifically, it relates to a process for treating an aluminum surface whereby the corrosion resistance and paint receptivity of the surface are improved.
Both alkaline and acidic aqueous solutions have been employed as cleaners for aluminum surfaces prior to further treatment. It has been proposed, for example in copending U.S. patent application Ser. No. 549,644, U.S. Pat. No. 3,969,135, that a cleaner for an aluminum surface may contain fluoride ion. It has also been proposed to employ an aqueous treating composition containing a vegetable tannin material in place of the conventional chromate phosphate aluminum treating bath. (See, for example, U.S. patent application Ser. No. 641,050 filed Dec. 15, 1975, Pat. No. 4,017,334, and a U.S. patent application in the name of King and Reghi filed concurrently herewith as a continuation-in-part of U.S. Ser. No. 612,075 filed Sept. 10, 1975, abandoned).